Indian Journal of Heterocyclic Chemistry
ISSN (Print) : 0971-1627 ISSN (Online) : 2456-4311
Vol. 27 - Number 03 (Jul-Sep 2017) 295-302
Study of the Catalytic Effect of Sodium Citrate on the Four-Component Synthesis of Pyrano[2,3-c]pyrazole Derivatives: An Eco-Friendly Method Rima Laroum, Chaïma Boureghda, Amina Benhadid, Raouf Boulcina, Abdelmadjid Debache* Laboratoire de synthèse de molécules d’intérêts biologiques, Université de Constantine 1, 25000 Constantine, Algérie
ABSTRACT An efficient and clean protocol was developed for the convenient synthesis of pyrano[2,3-c] pyrazoles via a one-pot four-component reaction of commercially available aldehydes, malononitrile, ethyl acetoacetate (or ethyl benzoylacetate), and hydrazine hydrate (or phenylhydrazine). The reactions were conducted in aqueous EtOH in the presence of sodium citrate as a catalyst. A series of pyrano[2,3-c] pyrazole derivatives were quickly obtained in excellent yields using this eco-friendly four-component onepot reaction.
KEY WORDS Multicomponent reaction, One-pot reaction, Pyrano[2,3-c]pyrazole, Sodium citrate, Eco-friendly catalyst.
INTRODUCTION Substituted pyrano[2,3-c]pyrazoles are important building blocks with rich bioactivity profile that includes anticancer,[1] anti-inflammatory,[2] antimicrobial,[3] analgesic properties,[4] Chk1 kinase inhibitory activity,[5] and also as biodegradable agrochemicals.[6] Potential biological activities and extensive synthetic utilities of pyranopyrazoles have led to their identification as a class of heterocyclic compounds, which has created considerable interest in the pharmaceutical industry and the diversified field of organic synthesis.[7] Furthermore, they play a significant role as important synthetic intermediates.[8] As a result, several strategies have been developed for the synthesis of pyranopyrazoles from the earlier reported multistep protocols[9,10] to multicomponent reactions.[11,12] A three-component reaction of aromatic aldehydes, malononitrile, and substituted pyrazolin-5-ones in ethanol medium was reported using triethylamine as a catalyst.[13] Recently, a four-component reaction of ethyl
acetoacetate, hydrazine hydrate, aldehydes, and malononitrile in the presence of (S)-proline under ultrasonic irradiation for the synthesis of functionalized 4H-pyrano[2,3-c]pyrazoles has been developed.[14] Some other base catalysts have been used for this condensation.[15] In addition, some environmentally friendly fourcomponent methods also have been developed by using catalysts such as L-proline,[16] γ-alumina,[17] amberlyst A21,[18] triethylamine,[19] and hexadecyl dimethyl benzyl ammonium chloride.[20] Recently, some other catalysts such as per-6-aminoβ-cyclodextrin,[21] basic ionic liquids,[22] or piperidine[23] were also used to achieve this transformation. Muramulla and Zhao[24] reported the first organocatalytic methods for asymmetric synthesis of dihydropyrano[2,3-c] pyrazoles. An efficient four-component reaction of dimethyl acetylenedicarboxylate, hydrazine hydrate, malononitrile, and aromatic aldehydes for the synthesis of 2,4-dihydropyrano[2,3-c]pyrazole-3-carboxylates in water has been also reported by Zonouz et al.[25]
*Corresponding author: E-mail:
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Indian Journal of Heterocyclic Chemistry Vol. 27, No. 03
Natural products have been used as catalysts in various organic transformations because of their easy handling and the absence of toxicity.[26] As part of our research program to develop selective, efficient green methods, and catalysts in organic synthesis,[27] we have been studied the catalytic effect of sodium citrate, an inexpensive, commercially available and environmentally friendly compound, for the synthesis of pyrano [2,3-c] pyrazoles, in a single step via four-component condensation involving aromatic aldehydes 1, malononitrile 2, ethyl acetoacetate 3a (or ethyl benzoylacetate 3b), and hydrazine hydrate 4a (or phenylhydrazine 4b) (Scheme 1).
RESULTS AND DISCUSSION The optimization of the operating conditions was performed using the model reaction involving benzaldehyde 1a (2 mmol), malononitrile 2 (2 mmol), ethyl acetoacetate 3a (2 mmol), hydrazine hydrate 4a (2 mmol), and sodium citrate (10 mol %) in solvent (5 ml) at different conditions (Scheme 1). We began by studying the effect of the temperature. Some reactions were performed at different temperatures (Table 1, entries 1-3). The best results were obtained in refluxing water. We then looked at the effect of the solvent on this four-component condensation. The execution of the model reaction under solvent-free conditions at 80°C, under refluxing ethanol, acetonitrile, dichloromethane or in 50% aqueous ethanol (Table 1, entries 4-8). A higher yield of 76% was obtained when aqueous ethanol was used (Table 1, entry 6). The reaction carried out without catalyst gave a yield of only 26% (Table 1, entry 14). To complete the optimization, the last tests were focused on the effect of the catalyst’s amount on the product yield, by varying the amount of sodium citrate from 5 to 50 mol% under the above conditions (Table 1, entries 9-13). The results showed that 5 mol% of the catalyst was sufficient to obtain product 5a an excellent yield of 80% (Table 1, entry 9). Once the optimal conditions were determined, we explored the scope and limitations of the one-pot reaction involving different aromatic or heteroaromatic aldehydes 1 bearing different substituents, malononitrile 2, β-ketoesters 3, and hydrazines 4. The results of the investigation involving the previous optimized conditions are presented in Table 2. In all cases, excellent yields with good selectivity were obtained. A possible reaction mechanism of this four-component reaction is illustrated in Scheme 2. Based on the chemistry of pyranopyrazoles, it is reasonable to assume that the resulting product is obtained from the condensation
between two key intermediates 1 and 2. The first pyrazolone intermediate 1 results from an initial condensation between ethyl acetoacetate and hydrazine hydrate, while the second is formed via a Knoevenagel reaction between aromatic aldehyde and malononitrile leading to an arylidene 2. The formation of these two intermediates is made easy with the assistance of the catalyst. The Michael adduct 3 is obtained from condensation between intermediates 1 and 2. Finally, intramolecular cyclization of adduct 3 leads after tautomerization, to the final target product 5.
EXPERIMENTAL Specified solvents and reagents were of reagent grade and used without further purification. 1H and 13C nuclear magnetic resonance (NMR) spectra were recorded as solutions on a BRUKER AVANCE DPX spectrometer at 250.13 and 62.5 MHz, respectively, using TMS as internal standard and DMSO-d6 as a solvent. Chemical shifts are reported in parts per million (ppm), and coupling constants (J) are reported in Hertz (Hz). Infrared (IR) spectra were obtained on potassium bromide (KBr) pellets with a Shimadzu Fouriertransform IR (FT-IR)-8201 PC spectrometer. Melting points were determined in a capillary tube and are uncorrected.
General procedure for the synthesis of dihydropyrano[2,3-c]pyrazoles: 5a-m In a 50 ml flask equipped with a magnetic stirrer was charged with an equimolar amount of the following reagents: Aldehyde 1, malononitrile 2, ethyl acetoacetate 3 (or ethyl benzoylacetate), hydrazine hydrate 4 (or phenylhydrazine), and 5 mol % of sodium citrate (catalyst) in aqueous ethanol (1:1) (5 ml). The mixture was heated with continued stirring at reflux until the reaction was complete (followed by thin layer chromatography, eluent: ethyl acetate/n-hexane: 1/2). After cooling, the reaction mixture was poured onto ice water and is stirred for 10-15 min; the obtained solid is then filtered and washed with cold water. Purification of the obtained products was carried out by crystallization from ethanol.
Data for selected products 6-amino-3-methyl-4-phenyl-2,4-dihydropyrano[2,3-c] pyrazole-5-carbonitrile (5a)
IR (KBr, cm−1): νmax = 3367; 3170; 2191; 1647; 1600; 1396. 1 H NMR: 1.77(s, 3H, CH3); 4.44 (s, 1H, CH); 6.64 (s, 2H, NH2); 7.13-7.3 (m, 5HAr); 11.98 (s, 1H, NH). 13C NMR: 8.33 (CH3); 35.02 (C4); 56.03 (C-CN); 95.94 (C-pyran); 119.36 (CN); 125.13 (C4’); 125.96 (C3’, C5’); 126.76 (C2’, C6’); 134.08 (C1’); 142.69 (C3); 153.34 (C-O); 159.36 (C-NH2).
Scheme 1: Synthesis of pyrano[2,3-c]pyrazoles catalyzed by sodium citrate 296
Rima Laroum et al. Table 1: Optimization of reaction conditionsa Entry
Solvent
1
Yieldb (%)
Catalyst (mol %)
Time (h)
Temperature (°C)
H2O
10
3
Ambient
53
2
H2O
10
1
50
40
3
H2O
10
1
Reflux
70 60
4
‑
10
1
80
5
EtOH
10
1
Reflux
39
6
EtOH/H2O
10
1
Reflux
76
7
CH2Cl2
10
1
Reflux
‑
8
CH3CN
10
1
Reflux
‑
9
EtOH/H2O
5
1
Reflux
80
10
EtOH/H2O
15
1
Reflux
69
11
EtOH/H2O
20
1
Reflux
76
12
EtOH/H2O
30
1
Reflux
76
13
EtOH/H2O
50
1
Reflux
73
14
EtOH/H2O
0
1
Reflux
26
a
Reaction conditions: Benzaldehyde 1a (2 mmol), malononitrile 2 (2 mmol), ethyl acetoacetate 3a (2 mmol), hydrazine hydrate (2 mmol), and sodium citrate (5‑50 mol %), bisolated yields (Part of Table 1)
Table 2: Synthesis of dihydropyrano[2,3‑c] pyrazoles catalyzed by sodium citrate Compound
Structure
Time (h)
Yield (%)
M.p. (°C) Measured
Reported
5a
1
80
246‑248
242‑244[28]
5b
2
62
200‑202
196‑198[22a]
5c
2
73
236‑238
233‑235[28]
5d
2
81
250‑252
249‑252[28]
(Contd...) 297
Indian Journal of Heterocyclic Chemistry Vol. 27, No. 03 Table 2: (Continued) Compound
Structure
Time (h)
Yield (%)
M.p. (°C) Measured
Reported
5e
2
71
225‑227
224‑226[22a]
5f
2
82
235‑236
232‑234[22a]
5g
3
84
214‑216
218‑220[27]
5h
2
84
162‑164
167‑169[29]
5i
3
87
214‑216
210‑212[30]
5j
2
94
202‑204
190‑191[30]
5k
1.5
50
>270
268‑270[19]
(Contd...) 298
Rima Laroum et al. Table 2: (Continued) Compound
Structure
Time (h)
Yield (%)
M.p. (°C) Measured
Reported
5l
3
56
268‑270
268‑270[31]
5m
1
72
254‑256
254‑256[3]
a
Reaction conditions: Aldehydes 1 (2 mmol), malononitrile 2 (2 mmol), ethyl acetoacetate 3a (or ethyl benzoylacetate 3b) (2 mmol), hydrazine hydrate 4a (or phenylhydrazine 4b) (2 mmol), and sodium citrate (5 mol %) in aqueous ethanol (5 ml) at reflux, bisolated yields
Scheme 2: Plausible mechanism of pyrano[2,3-c]pyrazoles synthesis 6-amino-3-methyl-4(4-methylphenyl)-2,4dihydropyrano[2, 3-c]pyrazole-5-carbonitrile (5b)
IR (KBr, cm−1): νmax = 3406; 3193; 2191; 1643; 1604; 1392. 1 H NMR: 1.68 (s, 3H, CH3); 2.24 (s, 3H, CH3); 4.35 (s, 1H, CH); 6.64 (s, 2H, NH2); 7.18 (m, 4HAr); 11.80 (s, 1H, NH). 13C NMR: 9.9 (CH3); 20.84 (CH3-Ar); 36.26 (C4); 58.99 (C-CN); 98.03 (C-pyran); 120.14 (CN); 121.58 (C4’); 128.05(C3’, C5’); 129.61 (C2’, C6’); 136.73 (C1’); 141.5 (C3); 155.82 (C-O); 161.59 (C-NH2).
ethyl acetoacetate (or ethyl benzoylacetate), and hydrazine hydrate (or phenylhydrazine) catalyzed by sodium citrate as an eco-friendly and inexpensive catalyst, commercially available, easy to handle. The significant advantages of this procedure are higher yields, quicker reactions, and a convenient and simple method.
REFERENCES [1]
Wang, J.L., Liu, D., Zheng, Z.J., Shan, S., Han, X., Srinivasula, S.M., Croce, C.M., Alnemri, E.S., Huang, Z. Structure-based discovery of an organic compound that binds Bcl-2 protein and induces apoptosis of tumor cells, Proc. Natl. Acad. Sci., U.S.A., 2000, 97, 7124–7129.
[2]
Zaki, M.E.A., Soliman, H.A., Hiekal, H.A., Rashad, A.E. Pyrazolopyranopyrimidines as a class of
CONCLUSION We have developed a new, highly efficient process for the synthesis of dihydropyrano[2,3-c]pyrazoles by a fourcomponent reaction with aromatic aldehydes, malononitrile,
299
Indian Journal of Heterocyclic Chemistry Vol. 27, No. 03 anti-inflammatory agents, Z. Naturforsch., 2006, C61, 1–5.
[3]
El-Tamany, E.S., El-Shahed, F.A., Mohamed, B.H. Synthesis and biological activity of some pyrazole derivatives, J. Serb. Chem. Soc., 1999, 64, 9–18.
[4]
Kuo, S.C., Huang, L.J., Nakamura, H. Studies on heterocyclic compounds. 6. Synthesis and analgesic and anti-inflammatory activities of 3,4-dimethylpyrano[2,3-c]pyrazol-6-one derivatives, J. Med. Chem., 1984, 27, 539–544.
[5]
Foloppe, N., Fisher, L.M., Howes, R., Potter, A., Robertson, A.G.S., Surgenor, A.E. Identification of chemically diverse Chk1 inhibitors by receptor-based virtual screening, Bioorg. Med. Chem., 2006, 14, 4792–4802.
[6]
(a) Junek, H., Aigner, H. Synthesen mit Nitrilen, XXXV. Reaktionen von tetracyanäthylen mit heterocyclen, Chem. Ber., 1973, 106, 914; (b) Wamhoff, H.; Kroth, E.; Strauch, K. Dihalogentriphenylphosphorane in der heterocyclensynthese. XXVII: Heterokondensierte 1, 2, 4-triazolo [1, 5-c] pyrimidine aus enaminonitrilen via O-ethylformimide, Synthesis, 1993, 11, 1129.
[7]
(a) Desai, N.C., Rajpara, K.M., Joshi, V.V. Synthesis of pyrazole encompassing 2-pyridone derivatives as antibacterial agents, Bioorg. Med. Chem. Lett., 2013, 23, 2714–2717; (b) Kupcewicz, B., Sobiesiak, K., Malinowska, K., Koprowska, K., Czyz, M., Keppler, B., Budzisz, E. Copper(II) complexes with derivatives of pyrazole as potential antioxidant enzyme mimics, Med. Chem. Res., 2013, 22, 2395–2402; (c) Martins, D.R., Pazini, F., Alves, V.D., de Moura, S.S., Liao, L.M., de Magalhaes, M.T.Q., Valadares, M.C., Andrade, C.H., Menegatti, R., Rocha, M.L. Synthesis, docking studies, pharmacological activity and toxicity of a novel pyrazole derivative (LQFM 021)-possible effects on phosphodiesterase, Chem. Pharm. Bull., 2013, 61, 524–531; (d) Purohit, M.K., Scovell, I., Neschadim, A., Katsman, Y., Branch, D.R., Kotra, L.P. Disulfide linked pyrazole derivatives inhibit phagocytosis of opsonized blood cells, Bioorg. Med. Chem. Lett., 2013, 23, 2324–2327.
[8]
[9]
[10]
300
Stachulski, A.V., Berry, N.G., Low, A.C.L., Moores, S.L., Row, E., Warhurst, D.C., Adagu, I.S., Rossignol, J.F.J. Identification of is flavone derivatives as effective anticryptosporidial agents in vitro and in vivo, Med. Chem., 2006, 49, 1450. (a) Ramon, D.J., Yus, M. Asymmetric multicomponent reactions (AMCRs): The new frontier, Angew. Chem., Int. Ed., 2005, 44, 1602; (b) Zhu, J. Recent developments in the isonitrile-based multicomponent synthesis of heterocycles, Eur. J. Org. Chem., 2003, 7, 1133; (c) Ugi, I., Domling, A., Werner, B. Since 1995 the new chemistry of multicomponent reactions and their libraries, including their heterocyclic chemistry, J. Heterocycl. Chem., 2000, 37, 647; (d) Bienayme, H., Hulme, C., Oddon, G., Schmitt, P. Maximizing synthetic efficiency: Multi-component transformations lead the way, Chem. Eur. J., 2000, 6, 3321. (a) Chebanov, V.A., Muravyova, E.A., Desenko, S.M., Musatov, V.I., Knyazeva, I.V., Shishkina, S.V., Shishkin, O.V., Kappe, C.O. Microwave-assisted three-component synthesis of 7-aryl-2-alkylthio-4, 7-dihydro-1, 2,
4-triazolo [1, 5-a]-pyrimidine-6-carboxamides and their selective reduction, J. Comb. Chem., 2006, 8, 427; (b) Dondoni, A., Massi, A., Sabbatini, S., Bertolasi, V. Three-component biginelli cyclocondensation reaction using c-glycosylated substrates. Preparation of a collection of dihydropyrimidinone glycoconjugates and the synthesis of c-glycosylated monastrol analogues, J. Org. Chem., 2002, 67, 6979; (c) Rashinkar, G., Salunkhe, R. Ferrocene labelled supported ionic liquid phase (SILP) containing organocatalytic anion for multi-component synthesis, J. Mol. Catal. A Chem., 2010, 316, 146; (d) Srihari, P., Singh, V.K., Bhunia, D.C., Yadav, J.S. One-pot three-component coupling reaction: Solvent-free synthesis of novel 3-substituted indoles catalyzed by PMA-SiO2, Tetrahedron Lett., 2009, 50, 3763. [11] (a) Muramulla, S., Zhao, C.G. A new catalytic mode of the modularly designed organ catalysts (MDOs): Enantioselective synthesis of dihydropyrano[2,3-c] pyrazoles. Tetrahedron Lett., 2011, 52, 3905–3908; (b) Parmar, N.J., Barad, H.A., Pansuriya, B.R., Talpada, N.P. A highly efficient, rapid one-pot synthesis of some new heteroaryl pyrano [2, 3-c] pyrazoles in ionic liquid under microwave-irradiation, RSC Adv., 2013, 3, 8064–8070. [12] (a) Sheibani, H., Babaie, M. Three-component reaction to form 1, 4-dihydropyrano [2, 3-c] pyrazol5-yl cyanides, Synth. Commun., 2010, 40, 257– 265; (b) Karimi-Jaberi, Z., ReyazoShams, M.M. Trichloroacetic acid as a solid heterogeneous catalyst for the rapid synthesis of dihydropyrano [2, 3-c] pyrazoles under solvent-free conditions, Heterocycl. Commun., 2011, 17, 177–179; (c) Azarifar, D., NejatYami, R., Sameri, F., Akrami, Z. Ultrasonic-promoted one-pot synthesis of 4H-chromenes, pyrano [2, 3-d] pyrimidines, and 4H-pyrano [2, 3-c] pyrazoles, Lett. Org. Chem., 2012, 9, 435–439; (d) Kumar, G.S., Kurumurthy, C., Veeraswamy, B., Rao, P.S., Rao, P.S., Narsaiah, B. Synthetic developments in functionalized pyrano [2, 3-c] pyrazoles, Org. Prep. Proced. Int., 2013, 45, 429–436. [13] Sharanin, Y.A., Sharanina, L.G., Puzanova, V.V.Z. Cyclization reactions of nitriles 7. Synthesis of 6-amino4-aryl-3-methyl-5-cyano-1H, 4H-pyyrazolo[3, 4-B] pyrans, Org. Khim., 1983, 19, 2609. [14] Khoobi, M., Ghanoni, F., Nadri, H., Moradi,A., Hamedani, M.P., Moghadam, F.H., Emami, S., Vosooghi, M., Zadmar, R., Foroumadi,A., Shafiee,A. New tetracyclic tacrine containing pyrano[2,3-c]pyrazole: Efficient synthesis, biological assessment and docking simulation study, Eur. J. Med. Chem., 2015, 89, 296–303. [15] (a) Al-Matar, H.M., Khalil, K.D., Adam, A.Y., Elnagdi, M.H. Green one pot solvent-free synthesis of pyrano [2, 3-c]-pyrazoles and pyrazolo [1, 5-a] pyrimidines, Molecules, 2010, 15, 6619–6629. (b) Litvinov, Y.M., Shestopalov, A.A., Rodinovskaya, L.A., Shestopalov, A.M. New convenient four-component synthesis of 6-amino-2,4-dihydropyrano[2,3-c] pyrazol-5-carbonitriles and one-pot synthesis of 6’-aminospiro[(3H)-indol-3,4’-pyrano[2,3-c]pyrazol](1H)-2-on-5’-carbonitriles, J. Comb. Chem., 2009, 11, 914–919. (c) Lehman, F., Holm, M., Laufer, S. Three-component combinatorial synthesis of novel dihydropyrano [2, 3-c] pyrazoles, J. Comb. Chem.,
Rima Laroum et al. 2008, 10, 364–367. (d) Peng, Y., Song, G., Dou, R. Surface cleaning under combined microwave and ultrasound irradiation: Flash synthesis of 4 H-pyrano [2, 3-c] pyrazoles in aqueous media, Green Chem., 2006, 8, 573–575. [16]
[17]
(a) Khurana, J.M., Nand, B., Kumar, S. Rapid synthesis of polyfunctionalized pyrano [2, 3-c] pyrazoles via multicomponent condensation in room-temperature ionic liquids, Synth. Commun., 2011, 41, 405–410; (b) Mecadon, H., Rohman, M.R., Kharbangar, I., Laloo, B.M., Kharkongor, I., Rajbangshi, M., Myrboh, B. L-proline as an efficicent catalyst for the multi-component synthesis of 6-amino-4-alkyl/ aryl-3-methyl-2, 4-dihydropyrano [2, 3-c] pyrazole5-carbonitriles in water, Tetrahedron Lett., 2011, 52, 3228–3231. Mecadon, H., Rohman, M.R., Rajbangshi, M., Myrboh, B. γ-alumina as a recyclable catalyst for the fourcomponent synthesis of 6-amino-4-alkyl/aryl-3-methyl2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles in aqueous medium, Tetrahedron Lett., 2011, 52, 2523–2525.
[18] Bihani, M., Bora, P.P., Bez, G., Askari, H. Amberlyst A21 catalyzed chromatography-free method for multicomponent synthesis of dihydropyrano[2,3-c] pyrazoles in ethanol, ACS Sustain. Chem. Eng., 2013, 1, 440–447. [19] Litvinov, Y.M., Rodinovskaya, L.A., Shestopalov, A.M. A new convenient four-component synthesis of 6-amino-2H, 4H-pyrano[2,3-c]pyrazole-5-carbonitriles and one-pot synthesis of 6’-amino-5-cyano-1,2dihydrospiro-[(3H)-indole-3,4’-(4’H)-pyrano[2,3-c] pyrazol]-2-ones, Russ. Chem. Bull. Int. Ed., 2008, 58, 2362–2368. [20]
Ablajan, K., Wang, L.J., Tuoheti, A., Kelimu, Y. An efficient four-component, one-pot synthesis of 6-amino4-Aryl-3-Methyl-2, 4-dihydropyrano [2, 3-C] pyrazole5-carbonitriles under phase-transfer catalyst, Lett. Org. Chem., 2012, 9, 639–643.
[21]
Kanagaraj, K., Pitchumani, K. Solvent-free multicomponent synthesis of pyranopyrazoles: Per-6amino-β-cyclodextrin as a remarkable catalyst and host, Tetrahedron Lett., 2010, 51, 3312–3316.
[22] (a) Khurana, J.M., Chaudhary, A. Efficient and green synthesis of 4 H-pyrans and 4 H-pyrano [2, 3-c] pyrazoles catalyzed by task-specific ionic liquid [bmim] OH under solvent-free conditions, Green Chem. Lett. Rev., 2012, 5, 633–638; (b) Li, X.J., Guo, H.Y. Onepot synthesis of 1,4-dihydropyrano[2,3-c]pyrazoles catalyzed by basic ionic liquids, Chin. J. Org. Chem., 2012, 32, 127–132. [23] Vasuki, G., Kumaravel, K. Rapid four-component reactions in water: Synthesis of pyranopyrazoles, Tetrahedron Lett., 2008, 49, 5636–5638. [24]
Gogoi, S., Zhao, C.G. Organocatalyzed enantioselective synthesis of 6-amino-5-cyanodihydropyrano [2, 3-c] pyrazoles, Tetrahedron Lett., 2009, 50, 2252–2255.
[25] Zonouz, A.M., Eskandari, I., Khavasi, H.R. A green and convenient approach for the synthesis of methyl 6-amino-5-cyano-4-aryl-2,4-dihydropyrano[2,3-c] pyrazole-3-carboxylates via a one-pot, multicomponent reaction in water, Tetrahedron Lett., 2012, 53, 5519–5522. [26]
(a) Patil, S., Jadhava, D.D., Deshmukhb, M.B. Natural acid catalyzed multi-component reaction as a green approach, Arch. Appl. Sci. Res., 2011, 3, 203–208. (b) Ramu, E., Kotra, V., Bansal, N., Varala, R., Adapa, S.R. Rasāyan, J. Green approach for the efficient synthesis of biginelli compounds promoted by citric acid under solvent-free conditions, J. Chem., 2008, 1, 188–194. (c) Nazeruddin, G.M., Shaikh, Y.I. Tamarind juice catalyzed one pot synthess of dihydropyrimidinone and thione under ultrasound irradiation at ambient conditions: A green approach, Der Pharm. Sin., 2014, 5, 64–68. (d) Zheng, J., Li, Y.Q. One-pot synthesis of tetrahydrobenzo[b]pyran and dihydropyrano[c] chromene derivatives in aqueous media by using trisodium citrate as a green catalyst, Arch. Appl. Sci. Res., 2011, 3, 381–388.
[27] (a) Debache, A., Ghalem, W., Boulcina, R., Belfaitah, A., Rhouati, S., Carboni, B. An efficient one-step synthesis of 1, 4-dihydropyridines via a triphenylphosphine-catalyzed three-component hantzsch reaction under mild conditions, Tetrahedron Lett., 2009, 50, 5248–5250. (b) Ghalem, W., Sedrati, R.H., Benloucif, N., Berrée, F., Boumoud, B., Debache, A. Triphenylphosphine-catalyzed one-pot three component synthesis of tetrahydrobenzo [b] Pyrans in aqueous medium, Lett. Org. Chem., 2013, 10, 150–154. (c) Amine-Khodja, I., Ghalem, W., Dehimat, Z., Boulcina, R., Carboni, B., Debache, A. Solvent-free synthesis of dihydropyridines and acridinediones via a salicylic acid-catalyzed hantzsch multicomponent reaction, Synth. Commun., 2014, 44, 959–967. (d) Amine-Khodja, I., Boulcina, R., Debache, A. Novel one-pot synthesis of 3, 4-dihydropyrimidin-2 (1H)-ones and 3, 4, 7, 8-tetrahydroquinazoline-2, 5-diones using pyridinium p-toluenesufonate as catalyst, Lett. Org. Chem., 2015, 12, 77–84. [28]
Moeinpour, F., Khojastechnezhad, A. Cesium carbonate supported on hydroxyapatite coated Ni0.5Zn0.5Fe2O4 magnetic nanoparticles as an efficient and green catalyst for the synthesis of pyrano[2,3-c]pyrazole, Chin. Chem. Lett., 2015, 26, 575–579.
[29]
Saha, M., Pal, A.K. Palladium (0) nanoparticles: A novel and reusable catalyst for the synthesis of various pyran derivatives, Adv. Nanopart., 2012, 1, 61–70.
[30] Jin, T.S., Zhao, R.Q., Li, T.S. An one-pot threecomponent process for the synthesis of 6-amino-4aryl-5-cyano-3-methyl-1-phenyl-1, 4-dihydropyrano [2, 3-c] pyrazoles in aqueous media, Arkivoc, 2006, 11, 176–182. [31] Zou, Y., Hu, Y., Liu, H., Shi, D.Q. An efficient and green synthesis of 6-amino-3-phenyl-4-aryl1,4-dihydropyrano [2,3-c]pyrazole-5-carbonitrile derivatives under ultrasound irradiation in aqueous medium, J. Heterocycl. Chem., 2013, 50, 1174–1179.
Received: 17 Jun 2017, Accepted: 18 Aug 2017
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